Bacteria Notes

Basic Definition• Bacteria: Prokaryotic Organisms– Pro: Primitive or “prior to”– Karyon: Nucleus or “kernel”– Single-celled organisms without a nucleus – Has circular DNA – Often has “plasmid” DNA that helps codes for genes to

increase fitness (ex. Antibiotic resistance)– Bacteria can be measured in micrometers• 0.000001m or 10-6

Prokaryo

What are the two groups of bacteria?

1. BacteriaCell walls with peptidoglycan

2. Archaebacteria• Cell walls lack peptidoglycan• Adapted to extreme environments:

Extremely hot and cold, salty, without oxygen, etc.

peptidoglycan

Made up of types of peptide and sugar bonds

What are the basic shapes of bacteria?

– Rod-shaped (Bacilli)Bacillus anthracis (Anthrax), Yersinia pestis (Bubonic plague)

– Comma-shaped (Vibrios) Vibrio cholerae– Spherical (Cocci)

Streptococcus, Staphylococcus– Spiral (Spirilla)

Treponema pallidum (Syphillis)

Bacterial Staining• Gram-positive: Retains the crystals of violet dye in the

peptidoglycan of the cell wall.

• Only has an inner layer of plasma membrane

• Infection by this type can be treated by antibiotics such as penicillin, which attacks the peptidoglycan of the cell wall.

• Gram-negative: Will not pick up much the violet dye because the cell wall is covered by an additional outer membrane, and instead appears pink.

• Infection by this type must be treated by a broad-spectrum antibiotic such as ciprofloxacin that enters bacteria and disrupts protein synthesis

Bacterial Staining

Peptidoglycan

Outer membrane

Inner membrane

What is a plasmid?• Plasmids are circles of DNA that can replicate

separately from the main bacterial DNA.• Plasmids may carry genes that allow bacteria

to survive exposure to antibiotics.

Bacterial Growth and Reproduction• Binary Fission: (video)

-Asexual division-DNA replicates and cytoplasm divides-Creates two genetically identical cells from one parent cell

• Conjugation: (video) -Not true sexual reproduction

-Sex pilus extends between bacteria -Plasmid DNA is transferred from one bacterium to another to introduce genetic diversity

• Spore Formation:-Occurs when growth conditions are unfavorable-An endospore is a “spore” with a thick internal wall of membrane that encloses and protects its DNA